This is a crossover that I've been considering for some time. It's not the first time I've attempted a crossover with Mass Effect. Indeed, those who have followed my Compost Heap will have probably seen Short Change Heroes, my attempt to crossover Mass Effect with the British science fiction series Blake's 7. And it's not my first attempt to cross it over with the Potterverse, with one of the attempts being a WBWL fic, though none of those efforts even reached the end of a chapter. However, Dis Lexic's 'Sirius' Old Flame' challenge provided the hook needed.

Now, it must be said that, as far as the Mass Effect universe is concerned, this is a massive AU. Tali was born over two centuries before she was supposed to, as is Garrus, Liara has a human father and was born in the 20th century, and the Reapers don't exist. This was inspired partly by Tellur's Blue Magic, as well as the Mass Effect stories of Gregg Landsman (I wholeheartedly recommend Mass Effect: Glorious Shotgun Princess, a crossover with the Exalted tabletop RPG that is awesome and hilarious: in what other story do you have Legion called Wuffles, Shepard capable of punchsploding her foes, and Liara melding with a living planet multiple times).

Also, I'm strongly considering having a Harry/Liara/Tali pairing, though if the story develops away from that, I'm leaning more towards a Harry/Tali pairing. Tali is adorable.

LOVING THE ALIENS

CHAPTER 1:

THE ALIENS

It was an action borne of desperation more than anything else. He stopped en route at a place he was sure wouldn't have anything ever again. It was an abandoned field not far from London, at the old Potter Estate, now in ruins thanks to Voldemort. He didn't come here to pay tribute to his parents and brother in all but blood, though. He came here partly out of wishful thinking.

He remembered when he and James, along with Lily, met the strange woman. Of the fantastic tale she had spun. It was an accident that they had met, but Sirius, oddly enough, had been drawn to that woman. Oh, he had pushed her away in the end, as the war against Voldemort came to a head, and he told her to leave before she got caught up…but it had been a brief but passionate affair.

Now, having escaped the Ministry's clutches again, thanks partly to his godson and that Hermione girl, he came here one last time, as a bit of a tribute…and perhaps he had been hoping he would see her again.

So he was surprised when, after he brought Buckbeak in to land, he saw a rather familiar mound where none should have been. And as he stared, a door opened on the side of the mound, light spilling out of it…and a familiar figure was silhouetted in the light. But she wasn't alone. A shorter figure, the size of a teenager, stood alongside her.

"…You came back?" Sirius breathed.

"Only today," the woman said. "It's been a long time, Sirius Black. The media intercept beacon I left last time caught wind of you being a fugitive, though. How in Athame's name did you end up a fugitive?"

"…Pettigrew betrayed us," Sirius said. "It's a long story."

"I'm sure it is. Incidentally…Little Wing…this is the one I spoke to you of," the woman said, speaking to the smaller figure. "This is your father."

Sirius blinked. He wasn't expecting this. He thought back to a night of passion, where he was told to 'embrace eternity', one last time before they parted ways. And as the smaller form walked up to him, tentatively, he stared. He couldn't help it. He was a father, even if it was…well, a strange child he now had.

"Hello," his daughter said, looking at him curiously. "You're my father?"

"…Yes, I am," Sirius said, almost choking up with emotion. So this was how James and Lily felt? He had a child, a daughter, and he hadn't even realised it…

Harry Potter was getting annoyed. Not that this was an uncommon state of affairs lately. After all, his so-called friends weren't contacting him. And Sirius hadn't responded to any of his letters ever since he escaped, even when he got entered into the Tri-Wizard Tournament. True, he was a fugitive on the run, and Harry knew getting mail to him would be tricky, but surely owl post would find him anywhere?

And now, here he was, kept in the dark, ever since being bundled off back to Little Whinging after Voldemort's return and Cedric's death. He was getting more and more irritated at the lack of news from Magical Britain.

So when he finally got a letter, Harry was almost tempted to throw it away in a fit of pique, even when he saw it was from Sirius. But eventually, curiosity won out, especially as it seemed to be printed on Muggle paper than scrawled on parchment.

I Solemnly Swear I Am Up To No Good,

First things first…I'm sorry, Harry. I was incommunicado when you were entered into that damned Tri-Wizard Tournament. Moony's filled me in on the details, and, well, I'm kicking myself for not being here to help you. I know that's probably little comfort to you, but it's the truth.

The reason why I was incommunicado is…well, it's complicated. You see, during the last war, I met a woman, a most extraordinary woman with whom I had a relationship with, a woman who had my child. Yes, I have a daughter, a lovely, beautiful and intelligent daughter. For the past year, we've been travelling. I can't give many details in this letter, probably because you won't believe me, but also because, well, it isn't safe.

I haven't been back in Britain for long. Bluntly, the Ministry is pillorying you in The Daily Prophet, calling Dumbledore a senile old fool and you an attention-seeking brat. Fudge is in denial about the Dark Wanker being back, and so he's engaging in character assassination. Still…it's past time, no matter what Dumbledore thinks, that you be trained. Dumbledore is hoping to ensure you don't have to fight any battles, but I think he's being an idiot.

Thanks to Moony, I've managed to bring in Hermione. The Weasleys, along with other associates of Dumbledore, are at a special HQ, which I can't say where. However, I'm bringing you here. I don't know what Dumbledore is thinking, leaving you with the Dursleys: I knew them before I was sent to Azkaban. But I'm with some people who are very interested in meeting you. I won't say who or what they are, as it's going to be a surprise.

I've enchanted the letter into becoming a Portkey. Activate it by saying 'Mischief Managed'. Pack your trunk first, though, and have Hedwig ready.

If you don't know whether it's me or not, remember that you and Hermione rescued me on Buckbeak.

Padfoot.

Harry looked at Hedwig, before he shrugged. While Pettigrew might have known the catchphrase of the Marauders, he wouldn't have known about Buckbeak. And if this did get him away from the Dursleys, then all the better. He might have a sixteenth birthday away from them, with his godfather. He was a bit annoyed that Sirius had been AWOL, true, but if he only just found out he had a daughter…

He packed quietly, and managed to get Hedwig into her cage, before holding onto the trunk and the cage, and murmured, "Mischief Managed." Then, the familiar hook-behind-the-navel sensation came about, and he was whisked away…

…Only to sprawl near what looked like a barrow. In the distance, as he got up woozily, he could see the ruins of an old manor house. He staggered about slightly, only for what seemed to be a door in the side of the barrow to slide up, and Remus stepped out, along with a rather punkish-looking woman with pink hair. Remus held out his wand at Harry. "What is your Patronus?"

"…A stag?" Harry said, bemused, only to see Remus and the young woman sigh in relief, and pocket their wands.

"Sorry, Harry," Remus said. "We just needed to be sure. You can't be too careful. This is Tonks, a relative of Padfoot's. While she is technically a member of the Order of the Phoenix, she opted to join us."

"Wotcher, Harry," the punkish woman said with a smile. "Just got to warn you, though…you're going to see some weird stuff in here. Like, weirder than Hogwarts."

"How so?" Harry asked. His anger was being replaced by curiosity.

Instead of answering, they gently escorted him into the door, which slid shut behind them. The room they were in was metallic and gleaming, and brightly lit. Harry knew that this couldn't be a wizarding place: he hadn't seen something so technological ever in Magical Britain.

A strange, distorted voice rang out, the voice apparently that of a girl's, but accented. "Beginning decontamination sequence." Beams of light ran up and down the occupants of the chamber. Eventually, the voice said, "All clear."

"…Why do I get the feeling I'm about to walk onto the set of an episode of Doctor Who?" Harry asked, with a sense of foreboding and curiosity.

"Oh, you don't know the half of it," Tonks said with a chuckle. Then, she said, "Hey, Tali, open up the door!"

The door slid open after a rather long pause, and Tonks and Remus went through, eventually followed by Harry, who stopped. And stared. Well, Toto, you're not in Kansas anymore, he thought.

The room beyond, while relatively small, was packed with instrumentation and control panels. Clearly it was in advance of pretty much everything Harry knew of on Earth. Manning one of the consoles was a figure in a figure-hugging spacesuit, apparently female with the hips and breasts, maybe about his age given the stature…with three fingers on her hands, three toes, and different legs that seemed to curve back before they connected to the ankle. Her helmet was purple, opaque save for a pair of glowing eyes. A light seemed situated about where the mouth was, and a veil or hood of some sort covered the top of the helmet.

It was clear that the figure wasn't human.

"Ah, you must be Harry," the girl said, her voice distorted by whatever she was using to speak from her suit, her accent having an exotically pleasant lilt. "A pleasure to meet you. I am Tali'Zorah nar Rayya. Tali for short."

She held out her hand, which Harry took, bemused. "…Uhh, hi. You're…not from around here, aren't you?"

"No. I am a Quarian. Which, as far as humans are concerned, means that I am an alien," Tali said.

"Told you he'd be speechless," Tonks said with a smirk. "Just don't stare too long, Harry. Tali's a bit shy."

And indeed, she was, Harry's scrutiny seemingly making the alien girl uncomfortable. "Oh, sorry."

Tali waved a hand. "It's fine. Once she got over her shock, your bushy-haired friend, Hermione, she began asking all sorts of questions. We'll get to talk later, but for now, I need to finish the maintenance here. One of the servos here is being a real bosh'tet."

"Tali's a mechanical wiz," Remus said, as he led Harry and Tonks away. "All Quarians have to be by necessity: they've lived on a massive spacefleet ever since their homeworld Rannoch was taken over by robots. Most of the other species out there don't think much of them, but a few have been brought along on this expedition."

"…Does that mean more aliens?" Harry asked.

"Yes. It's not an invasion, Harry. It's more like an off-the-books expedition to study humans and our culture," Remus said. "Earth is far enough away from what is called Citadel Space that it would take time to come here normally. Oh, Wrex!"

Harry stopped and stared. What was lumbering towards them was a massive, reptilian creature with a humped back, dressed in futuristic armour, with red skin. "Lupin," he rumbled. "Is this the kid?"

"Yes. Harry, this is Urdnot Wrex, a Krogan."

Harry offered his hand, even more apprehensive than when he met Tali, and felt his hand enveloped in the clawed paw of Wrex. "Good to meet you, kid. You're reacting better than the werewolf and Nymphadora here did when they met me. The werewolf damn near pissed himself, and the girl's hair turned white. You've got a quad on you, no mistake."

Harry didn't think so, whatever a quad was, though he could hazard a guess from context. He wondered why he had called Tonks Nymphadora. "Uhh, thanks?"

A rumbling laugh came from the reptilian creature. "I'd better go and see if Varkarian's finished his endless recalibrations on our guns. He ain't too bad for ex-C-Sec." And with that, he lumbered off.

"…Next time he calls me Nymphadora, I'm gonna hex his goddamn quads off," Tonks growled. "Regeneration abilities or not."

"There's at least five different types of aliens in this expedition, not counting humans," Remus said as they started off down the corridor again. "Garrus Varkarian is one of two Turians on the expedition. We also have a Salarian and a few Asari. Don't worry, you'll see them."

"…Okay, so, Sirius said he had a former lover and a daughter," Harry said.

"Nothing former about it," Tonks snorted. "We've had to place silencing charms on their room, given how many times they've 'embraced eternity'. They've been catching up. Then again, he didn't get any in Azkaban…I'm surprised she isn't pregnant again. She's apparently a bigwig amongst the Asari, tipped to become one of their leaders soon."

They came to a door, which slid open, and Harry was promptly attacked by a bushy-haired missile. "Harry!" it cried, embracing him.

Harry looked down to see the familiar features of Hermione Granger looking up at him, smiling. "Hey, Hermione. How dare you get to meet aliens before me?"

His earlier anger had been mostly washed away by the sheer shock of meeting aliens, so his jibe was meant to be facetious. But Hermione flinched anyway. "Sorry. I've only been here for a couple of days. So have my parents. Originally…Dumbledore told me not to write to you, to let you mourn in peace. That was a mistake. Anyway, I've spent a lot of time learning about this, and…oh! I forgot to introduce you two."

Harry realised that they were in some sort of large room, centred around a table with holograms hovering above it. There was only one other occupant of the room, at least for now…and it was another alien.

Harry couldn't help but stare, even though he had been, understandably, doing that a lot. Although this was not just out of any mere strangeness. The alien, a girl about their age like Tali, was also one of the most beautiful people he had ever seen. True, she had blue skin, and strange tendril-like crests instead of hair, and she was dressed in a rather utilitarian outfit that looked like some kind of plastic, but her face was utterly breathtaking.

"Can I introduce myself, Hermione?" the girl asked, as she got up and walked over to Harry.

"Sure."

"Thank you." She smiled at Harry. "It's a pleasure to meet you, Harry. My name is Liara T'Soni, and my father is your godfather…"

CHAPTER 1 ANNOTATIONS:

Wow. So, Sirius' former paramour is Benezia, and his daughter is Liara? Just remember, I've done a lot of tinkering with the Mass Effect timeline. Liara and Tali are teenagers about Harry and Hermione's age, Garrus and Mordin are both around at their standard ages, and…well, Wrex and a couple of the Asari characters could be around, given their ages. No Reapers, though. Fuck the Reapers. The Protheans died out because of a collapse of their empire and other factors. Then again, considering what they turned out to be like in canon, if Javik's any indication, I find myself not giving a fuck.

No numbered annotations this time.